diff --git a/include/mbedtls/des.h b/include/mbedtls/des.h
index 92da73f..24d2402 100644
--- a/include/mbedtls/des.h
+++ b/include/mbedtls/des.h
@@ -26,6 +26,7 @@
  */
 #ifndef MBEDTLS_DES_H
 #define MBEDTLS_DES_H
+#include "mbedtls/private_access.h"
 
 #if !defined(MBEDTLS_CONFIG_FILE)
 #include "mbedtls/config.h"
@@ -60,7 +61,7 @@
  */
 typedef struct mbedtls_des_context
 {
-    uint32_t sk[32];            /*!<  DES subkeys       */
+    uint32_t MBEDTLS_PRIVATE(sk)[32];            /*!<  DES subkeys       */
 }
 mbedtls_des_context;
 
@@ -69,7 +70,7 @@
  */
 typedef struct mbedtls_des3_context
 {
-    uint32_t sk[96];            /*!<  3DES subkeys      */
+    uint32_t MBEDTLS_PRIVATE(sk)[96];            /*!<  3DES subkeys      */
 }
 mbedtls_des3_context;